Water vehicles

ABSTRACT

Equipment and methods that combine the use of wave powered vehicles and unmanned aerial vehicles (UAVs or drones). A UAV can be launched from a wave-powered vehicle, observe another vessel, and report the results of its observation to the wave-powered vehicle, and the wave-powered vehicle can report the results of the observation to a remote location. The UAV can land on water and can then be recovered by the wave-powered vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following U.S. and Internationalpatents and patent applications

-   U.S. patent application Ser. No. 11/436,447, filed May 18, 2006, now    U.S. Pat. No. 7,371,136,-   U.S. patent application Ser. No. 12/082,513, now U.S. Pat. No.    7,641,524,-   International Patent Application No. PCT/US 07/01139, filed Jan. 18,    2007, published Aug. 2, 2007, as WO 2007/087197,-   International Patent Application No. PCT/US 2008/002703, filed Feb.    29, 2008, published Sep. 12, 2008, as WO 2008/109002,-   U.S. patent application Ser. No. 13/424,156, filed Mar. 19, 2012,-   U.S. patent application Ser. No. 13/424,170, filed Mar. 19, 2012,-   U.S. patent application Ser. No. 13/424,312, filed Mar. 19, 2012,-   U.S. patent application Ser. No. 13/536,935 filed Jun. 28, 2012,-   U.S. patent application Ser. No. 13/621,803, filed Sep. 17, 2012,-   International Patent Application PCT/US 2012/029696, filed Mar. 19,    2012,-   International Patent Application PCT/US 2012/029718, filed Mar. 19,    2012,-   International Patent Application PCT/US 2012/044729, filed Jun. 28,    2012,-   International Patent Application PCT/US 2012/055797, filed Sep. 17,    2012,-   U.S. Provisional Patent Application No. 60/760,893, filed Jan. 20,    2006,-   U.S. Provisional Patent Application No. 60/904,647, filed Mar. 2,    2007,-   U.S. Provisional Patent Application No. 60/841,834 filed Sep. 1,    2006,-   U.S. Provisional Patent Application No. 60/904,647, filed Mar. 2,    2007,-   U.S. Provisional Patent Application No. 61/453,871, filed Mar. 17,    2011,-   U.S. Provisional Patent Application No. 61/453,862, filed Mar. 17,    2011,-   U.S. Provisional Patent Application No. 61/502,279, filed Jun. 28,    2011,-   U.S. Provisional Patent Application No. 61/535,116, filed Sep. 15,    2011,-   U.S. Provisional Patent Application No. 61/573,755, filed Sep. 12,    2011,-   U.S. Provisional Patent Application No. 61/585,229, filed Jan. 10,    2012, and-   U.S. Provisional Patent Application No. 61/600,556, filed Feb. 17,    2012.    The entire disclosure of each of those patents, applications and    publications is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

This invention relates to autonomous water vehicles.

As a wave travels along the surface of water, it produces verticalmotion, but no net horizontal motion, of water. The amplitude of thevertical motion decreases with depth; at a depth of about half the wavelength, there is little vertical motion. The speed of currents inducedby wind also decreases sharply with depth. A number of proposals havebeen made to utilize wave power to provide useful results. Reference maybe made, for example, to the patents and applications incorporated byreference above, and to U.S. Pat. Nos. 986,627, 1,315,267, 2,520,804,3,312,186, 3,453,981, 3,508,516, 3,845,733, 3,872,819, 3,928,967,4,332,571, 4,371,347, 4,389,843, 4,598,547, 4,684,350, 4,842,560,4,968,273, 5,084,630, 5,577,942, 6,099,368 and 6,561,856, U.S.Publication Nos. 2003/0220027 and 2004/0102107, WO 94/10029 and WO87/04401. The entire disclosure of each of those patents, patentapplications and publications is incorporated herein by reference forall purposes.

Liquid Robotics, Inc. has developed particularly useful water vehicles(“Wave Gliders”®), as described for example in U.S. Pat. Nos. 7,641,524and 8,043,133, which are autonomous (i.e. which do not carry a humanbeing) and which can traverse the oceans for long periods of time underthe direction of signals sent to the vehicle from a control location,while gathering useful information which can be communicated to areception location and/or recorded.

SUMMARY OF THE INVENTION

The term wave-powered vehicle (often abbreviated to WPV) is used in thisspecification to denote an autonomous water vehicle which comprises

-   (1) a float which can float on or near the surface of water,-   (2) a swimmer,-   (3) a flexible or rigid tether connecting the float and the swimmer,-   (4) a computer system,-   (5) a satellite-referenced position sensor on the float,-   (6) a horizontal sensor which senses direction in a horizontal    plane,-   (7) a steering actuator,-   (8) means for converting solar energy and/or wind power anchor wave    power into electrical power,-   (9) batteries which can be charged by the means for converting solar    energy and/or wind power and/or wave power into electrical power,    and-   (10) communications equipment for receiving and/or sending signals    from a remote location, for example a location on land or on another    water vehicle;    the computer system (i) being linked to the position sensor, the    horizontal sensor and the steering actuator, and (ii) containing, or    being programmable to contain, instructions to control the steering    actuator in response to signals received from the position sensor    and the horizontal sensor or in response to signals received from an    additional sensor (i.e. a sensor which is not the position sensor or    the horizontal sensor); and the float, swimmer and tether being such    that-   (A) when the vehicle is in still water and the float is on or near    the surface of the water, the swimmer is submerged below the float,    and the tether is under tension; and-   (B) when the vehicle is in wave-bearing water and the float is on or    near the surface of the water, the swimmer interacts with the water    to generate forces which move the float in a direction having a    horizontal component (hereinafter referred to simply as “in a    horizontal direction” or “horizontally”).

A WPV can comprise a single one of each of the named components(1)-(10), or two or more of one or more of the named components; forexample, there can be two or more floats (as in a catamaran) and/or twoor more tethers. The means for converting solar energy and/or wind powerand/or wave power into electrical power can for example include one ormore of (a) solar panels (photovoltaic (b) a wind mill, and (c) use offorward motion of the vehicle to turn a water mill connected to agenerator.

The term UAV is used in this specification to denote an unmanned aerialvehicle (UAVs are often referred to as drones).

In various ways, as described in detail below, this invention makes useof equipment and methods which combine the use of wave powered vehiclesand unmanned aerial vehicles (UAVs or drones). A UAV can be launchedfrom a wave-powered vehicle, observe another vessel and report theresults of its observation to the wave-powered vehicle and thewave-powered vehicle can report the results of the observation to aremote location. The UAV can land on water and can then be recovered bythe wave-powered vehicle.

SUMMARY OF THE DIFFERENT ASPECTS OF THE INVENTION

This invention relates to:

In a first aspect, a float which comprises means for launching a UAV.Some of the floats of the first aspect of the invention are equippedwith some or all of the components (4)-(10) listed above. Others aresuitable for use in WPVs only after they have been equipped withequipment which makes the float suitable for use in a WPV. Others aredesigned to be towed behind a WPV.

In a second aspect, a WPV which comprises a float according to the firstaspect of the invention.

In a third aspect, a WPV which comprises means for recovering a UAVwhich is floating in the water.

In a fourth aspect, a float which comprises means for recovering a UAVwhich is floating in the water. Some of the floats of the fourth aspectof the invention are equipped some or all of the components (4)-(10)listed above. Others are suitable for use in WPVs only after they havebeen equipped with equipment which makes the float suitable for use in aWPV.

In a fifth aspect, this invention provides a method of monitoringvessels which are floating in water, the method comprising receivingcommunications from a UAV on the communications equipment of the WPV,and transmitting corresponding communications to a receiving station ata remote location, for example a receiving station on land or on anothervessel (including another WPV).

In a sixth aspect, this invention provides a method of monitoring avessel which is floating in water, the method comprising correlatingsignals received by a plurality of WPVs to identify the location of thevessel, and launching a UAV from a WPV according to the first aspect ofthe invention to the location of the vessel.

In a seventh aspect, this invention provides a UAV which, when it landson water, sinks below the surface of water except for a recovery meanswhich remains above the surface of the water.

In an eighth aspect, this invention provides a UAV which can beconverted between (1) a collapsed form in which it can be stowed in atube and (2) an unfolded form which can operate as a UAV and which theUAV adopts automatically when it is released from the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the accompanying drawings, which areincluded by way of example only, and are diagrammatic and not to scale.In the drawings:

FIG. 1 is a perspective view of a WPV having a recovery cable extendingfrom the swimmer for recovering a UAV which is floating in water;

FIG. 2 is a side view of a tube and a UAV in a collapsed form which isstowed in the tube; in FIG. 2, the tube, which would not normally betransparent, is shown as transparent in the interests of clarity;

FIG. 3A is a side view, FIG. 3B is a front view, FIG. 3C is a top view,and FIG. 3D is a perspective view, of a UAV which has unfolded afterbeing launched from a tube;

FIG. 4 is a view of a WPV having a recovery cable extending from thefloat for recovering a UAV;

FIG. 5 illustrates how a UAV which has landed in the ocean and which isbelow the surface of the water except for a hook which can engage arecovery cable extending from a WPV;

FIG. 6 illustrates a float which can be part of a WPV and which hecomprises means for launching a UAV; and

FIG. 7 illustrates a float which can be part of a WPV and an auxiliaryfloat which comprises means for launching a UAV and which is connectedto and pulled behind the WPV.

DETAILED DESCRIPTION OF THE INVENTION

In the Summary of the Invention above, in the Detailed Description ofthe Invention below, and in the accompanying drawings, reference is madeto particular features (including for example components, ingredients,elements, devices, apparatus, systems, groups, ranges, method steps,test results, etc.) of the invention. It is to be understood that thedisclosure of the invention in this specification includes all possiblecombinations of such particular features. For example, where aparticular feature is disclosed in the context of a particular aspect ora particular embodiment, that feature can also be used in combinationwith other particular aspects and embodiments, and in the inventiongenerally, except where the context excludes that possibility. Theinvention disclosed herein include embodiments not specificallydescribed herein and can for example make use of features which are notspecifically described herein, but which provide functions which are thesame, equivalent or similar to, features specifically disclosed herein.

The term “comprises” and grammatical equivalents thereof are used hereinto mean that, in addition to the features specifically identified, otherfeatures are optionally present. For example, a composition or device“comprising” (or “which comprises”) components A, B and C can containonly components A, B and C, or can contain not only components A, B andC but also one or more other components. The term “consistingessentially of” and grammatical equivalents thereof is used herein tomean that, in addition to the features specifically identified, otherfeatures may be present which do not materially alter the claimedinvention. The term “at least” followed by a number is used herein todenote the start of a range beginning with that number (which may be arange having an upper limit or no upper limit, depending on the variablebeing defined). For example “at least 1” means 1 or more than 1, and “atleast 80%” means 80% or more than 80%. The term “at most” followed by anumber is used herein to denote the end of a range ending with thatnumber (which may be a range having 1 or 0 as its lower limit, or arange having no lower limit, depending upon the variable being defined).For example, “at most 4” means 4 or less than 4, and “at most 40%” means40% or less than 40%. When a range is given as “(a first number) to (asecond number)” or “(a first number)-(a second number)”, this means arange whose lower limit is the first number and whose upper limit is thesecond number. The terms “plural”, “multiple”, “plurality” and“multiplicity” are used herein to denote two or more than two features.

Where reference is made herein to a method comprising two or moredefined steps, the defined steps can be carried out in any order orsimultaneously (except where the context excludes that possibility), andthe method can optionally include one or more other steps which arecarried out before any of the defined steps, between two of the definedsteps, or after all the defined steps, except where the context excludesthat possibility. Where reference is made herein to “first” and “second”features, this is generally done for identification purposes; unless thecontext requires otherwise, the first and second features can be thesame or different, and reference to a first feature does not mean that asecond feature is necessarily present (though it may be present). Wherereference is made herein to “a” or “an” feature, this includes thepossibility that there are two or more such features (except where thecontext excludes that possibility). Where reference is made herein totwo or more features, this includes the possibility that the two or morefeatures are replaced by a lesser number or greater number of featuresproviding the same function, except where the context excludes thatpossibility. The numbers given herein should be construed with thelatitude appropriate to their context and expression; for example, eachnumber is subject to variation which depends on the accuracy with whichit can be measured by methods conventionally used by those skilled inthe art.

If any element in a claim of this specification is considered to be,under the provisions of 35 USC 112, an element in a claim forcombination which is expressed as a means or step for performing aspecified function without the recital of structure, material, or actsin support of thereof, and is, therefore, construed to cover thecorresponding structure, material, or acts described in thespecification and equivalents thereof, then the corresponding structure,material, or acts in question include such structure, material, or actsdescribed in the US patent documents incorporated by reference hereinand the equivalents of such structure, material, or acts.

When reference is made herein to a plan view, a side view, or an endview, or to a cross-section of a float, or to a component of a floatbeing at an angle to the horizontal or to the vertical, the float isbeing viewed in its normal horizontal position when it is floating onstill water (i.e. water which is free from waves).

This specification incorporates by reference all documents referred toherein and all documents filed concurrently with this specification orfiled previously in connection with this application, including but notlimited to such documents which are open to public inspection with thisspecification.

(A) The First Aspect of the Invention

The first aspect of the invention is a float which comprises means forlaunching a UAV. The means for launching the UAV preferably comprises alaunch tube which contains a collapsed UAV according to the eighthaspect of the invention or into which a collapsed UAV according to theeighth aspect of the invention can be loaded. The tube contains amechanism which will eject a collapsed UAV from the tube. The mechanismcan for example comprise one or more of a pre-loaded spring, bungeeelastic, compressed air, or a pyrotechnic.

In one embodiment, the means for launching the UAV is part of a floatwhich can be connected by a tether to a swimmer and which is optionallyequipped with some or all of the components (4)-(10) listed above. Inanother embodiment, the means for launching the UAV is part of anauxiliary float which is designed to be connected to and pulled behind afloat which is part of a WPV. In use, the auxiliary float is connectedto the float by a cable. Preferably the cable contains componentsthrough which a signal can be sent to the tube(s) on the auxiliaryvessel to launch a collapsed AUV from the tube. Alternatively, the tubeis equipped with components which can receive a signal from the WPV tolaunch the AUV.

The tube is set at an angle to the horizontal, for example an angle of30-60°, e.g., about 45°, so that the UAV is ejected from the tube clearof the water. When the tube is mounted on the WPV itself, it ispreferably mounted at the front of the float, so that when the UAV islaunched, it does not collide with any antenna or other component abovethe top surface of the float. When the tube is mounted on an auxiliaryfloat, it can be mounted anywhere on the auxiliary float which ensuresthat the launched AUV does not collide with any part of the WPV itself,for example pointing directly away from the WPV. The tube can comprisecomponents which compensate for movement of the WPV or auxiliary floataway from the horizontal, either purely mechanically or through acombination of mechanical and software components.

There can be a battery of such tubes, e.g., 4-8 tubes. For example, 6tubes may be arranged 2 wide by 3 deep, all angled at about 45 degreesaway from the superstructure on the WPV float, so that the launch pathof the drone stays clear of the antennae of the float.

The launch tube is preferably cylindrical and has sealable end caps sothat it can keep the drone dry.

(B) The Second Aspect of the Invention

The second aspect of the invention provides a WPV which comprises afloat according to the first aspect of the invention. As noted above,the float can be a float which is connected by a tether to a swimmer oran auxiliary float which is towed behind that float.

(C) The Third Aspect of the Invention

The third aspect of the invention is a WPV which comprises means forrecovering a UAV, particularly a UAV which is floating in the water.Preferably the WPV is equipped with a recovery cable which can bereleased (from the float or the swimmer) and which comprises a terminalportion which will float on the surface of the water. The terminalportion has a length of, for example, 10-100 m. After the recovery cablehas been released, the WPV is directed to move in a partial or completecircle (or other generally closed figure) around the UAV which isfloating in the water. The terminal portion of the recovery cable movesin a corresponding but smaller route, and thus contacts the floatingUAV. Having orbited the UAV with its recovery cable sweeping over theAUV, the WPV can continue on its previous heading and a force sensingswitch on a winch connected to the recovery cable can detect asuccessful hook engagement and start the winch. Another sensor coulddetect the arrival of the UAV at the WPV to stop the winch.

Either or both of the terminal portion and the UAV comprise componentswhich cause the terminal portion and the UAV to be connected to eachother. The recovery cable is then reeled in so that the UAV can besecured to the WPV. The amount of information that can be transmittedfrom an AUV to a WPV (or other receiving station) is less than theamount of information that can be stored on the AUV itself. It is,therefore, useful to be able to recover the AUV, not only to reuse theAUV (if that is possible) but also to recover the information which isstored in it. Thus, data can be collected on flash drives or by camerasor by other sensors on an AUV at much higher rates than can beeffectively transmitted via radio links. For example, an AUV can shootvery high resolution video and store it on micro SD cards with many GBcapacity. This data may be very valuable to collect, but is verydifficult to transmit wirelessly to a WPV because it takes a long timeand lots of power to transmit via wifi.

In one embodiment, the recovery cable is ejected from a tube from whichan AUV has been ejected, and the recovered AUV is reinstalled in thetube.

In another alternative, the wings of the AUV have hooks on their forwardedges. The AUV is deliberately flown into a mast or line projecting fromthe float of the WPV. The hooks engage the mast or line and the AUVcircles around the mast or line until it lands on the float.

The ability to recover the AUV after it has made a crash landing on thewater means that the AUV can use nearly all of its battery power on itsmission (it doesn't need a reserve to make multiple landing attempts).Weather and sea conditions may be poor, but because the WPV does not runout of power, it can make several attempts (which may take a very longtime—months even) to recover the AUV.

(D) The Fourth Aspect of the Invention

The fourth aspect of the invention is a float which comprises means forrecovering a UAV which is floating in the water. The means is preferablya recovery cable as disclosed in the discussion of the third aspect ofthe invention. Some of the floats of the fourth aspect of the inventionare equipped with sonic or all of the components (4)-(10) listed above.Others are suitable for use in WPVs only after they have been equippedwith equipment which makes the float suitable for use in a WPV.

(E) The Fifth Aspect of the Invention

The fifth aspect of the invention is a method of monitoring vesselswhich are floating in water, the method comprising receivingcommunications from a UAV on the communications equipment of the WPV,and transmitting corresponding communications from the WPV to areceiving station at a remote location, for example a receiving stationon land or on another vessel (including another WPV). It is of coursepossible to make an AUV which will fly over long distances and receiveand transmit information from and to distant locations. However, suchAUVs are expensive. The present invention makes it possible to employrelatively cheap AUVs, since the AUV is not released until it isrelatively close to the target to be observed, and can make use ofrelatively cheap communications equipment which can supply informationto the WPV from which the AUV has been released. A highly effective AUVcould comprise low-cost cameras and RC hobby type components, which arerapidly gaining in sophistication and capability. The WPV, which isequipped with more robust communications equipment, can then transmitthe information to a distant location.

(F) The Sixth Aspect of the Invention

The sixth aspect of the invention is a method of monitoring a vesselwhich is floating in water, the method comprising correlating signalsreceived by a plurality of WPVs to identify the location of the vessel,and launching a UAV from a WPV according to the first aspect of theinvention to observe the vessel. In this method, two or more WPVsreceive signals which indicate the presence of the vessel, and theequipment on the WPVs makes it possible to determine the location of thevessel. Depending upon the signals received by the WPVs, for the vesselmay be, for example, 3-40 miles, for example 10-25 miles, from one orboth of the WPVs.

Thus, a WPV may carry acoustic sensors that detect the presence andbearing of a target (like an illegal fishing boat or possible smuggler)that may be several miles—perhaps 20 miles away. Multiple wave glidersmay work together and from the intersection of two bearing lines,determine the location of a target. Even in foul weather and under thecover of night, cloud and rain, such WPVs could collect acoustic datasuggesting the presence and location of a hostile or illegal target inan area that is otherwise difficult to patrol by ship, plane orsatellite. Similarly, wave gliders may collect radio signals e.g., froma ship's s radar and determine the bearing of a ship that may be manymiles away and even over the horizon. However, it will often beimpossible to determine the identity or purpose of such a target fromacoustic and RF information alone. This invention makes it possible tosend relatively inexpensive AUV to observe the target and obtain furtherinformation which can be sent back to the WPV. This is much lessexpensive and time consuming than investigation by manned water vehiclesand/or long range UAVs launched from shore.

For civilian applications in particular (such as Marine Protected Areaenforcement), a disposable or single-use AUV would have sufficientcapability.

(G) The Seventh Aspect of the Invention

The seventh aspect of the invention is a UAV which, when it lands onwater, sinks below the surface of water except for a recovery meanswhich remains above the surface of the water. The recovery means can bea hook or other engagement mechanism. The hook can for example beattached to the front or back of the body of the AUV when the AUV isin-flight, or it can be released only after the AUV has contacted thewater. In one embodiment, the AUV, after it has contacted the water,ejects a lifeline which terminates in a buoy which remains on thesurface of the water and which can transmit signals to identify itslocation. Preferably the float comprises means for engaging a line whichcontacts the float. When the line brushes by the AUV, the hook or otherengagement means snaps shut and grips the line. The AUV itself, or thebuoy ejected from it, may have a beacon (RF, acoustic or light beacon)or may be able to send a GPS (or similar) message on its location sothat the WPV can home in on the UAV.

In one embodiment, a retrieval hook attaches to the inboard, aft cornersof each wing root and to the middle of over-center links which maintainthe wings are in the correct flying position. As a result, when the hookis pulled forward in the course of the recovery of the AUV, the wingsfold backwards together, minimizing the cross section of the AUV.Similarly the propeller folds as soon as the engine stops. Similarly thepropeller folds as soon as the engine stops.

Instead of towing a recovery line, the WPV may extend an appendage toone side or the other to capture the AUV.

(H) The Eighth Aspect of the Invention

The eighth aspect of the invention is an UAV which can be convertedbetween (1) a collapsed form in which it can be stowed in a tube and (2)an unfolded form which can operate as a UAV and which the UAV adoptsautomatically when it is released from the tube. The UAV preferably fitsinside a tube which generally, but not necessarily, has a substantiallycircular cross-section. The wings of the UAV can then fold and stacknear the center-line of the tube so that the wing chord length can bemaximized for a given diameter of tube. When the AUV is ejected from thetube, a spring (which may be a disposable spring) unfolds the AUV andspreads its wings to their flying configuration, which is maintained byover-center links. [These over-center links may be disabled duringrecovery of the AUV so that the wings can fold during retrieval]. Thepropeller automatically unfolds to provide thrust when rotated by amotor which is timed to start after the wings have unfolded. The UAVthen navigates towards its first heading and altitude.

In one embodiment, the UAV comprises over-lapping wings that pivothorizontally backwards on the same centerline, vertical axis hinge. Theadvantage of this design is a reduction in the diameter of the foldedpackage (tube) while maximizing the wing area available. The fact thatthe wings are vertically displaced by one wing root thickness is of nosignificant consequence at the low airspeeds on the UAVs which arepreferably employed in this invention. Careful fairing of the wing tofuselage shape is preferably employed to minimize parasitic drag at thisjunction.

In some embodiments, there are downward sloping fins on the wingtips,each having a controllable elevator/rudder that can be moved via controlcables from wing root actuators. Such downward sloping fins minimizeinterference with the tow line and its hooks during retrieval and willhelp guide the tow line to slide over the AUV until it catches theretrieval hook.

Referring now to the drawings, FIG. 1 shows a WPV 1 comprising a float11, a swimmer 12 and a tether 13 connecting the float and swimmer. Thefloat includes a satellite-referenced position sensor 15 extendingupwards from the float, antenna 119 extending upwards from the float,solar cells 18 exposed on the top of the float, and under the solarcells, and not visible in the FIG., a computer system 14, a horizontalsensor which senses direction in a horizontal plane 16, batteries 19which can be charged by the solar cells, and communications equipment110. The swimmer includes a recovery cable 120 having a terminal portion121 which will float on the surface of water.

FIG. 2 shows a tube 3 with a collapsed UAV 2 within it.

FIG. 3A is a side view, FIG. 3B is a front view, FIG. 3C is a top view,and FIG. 3D is a perspective view, of a UAV which has unfolded afterbeing launched from a tube. The UAV comprises wings 21 which haveunfolded from the collapsed configuration shown in FIG. 2 in which theyare aligned over each other. The UAV also comprises a propeller 22 whichhas unfolded from the collapsed configuration of the UAV shown in FIG.2.

FIG. 4 shows a float 1 which includes a recovery cable 120 having aterminal portion 121 which will float on the surface of water.

FIG. 5 shows a UAV which, after landing in the ocean (for example crashlanding after becoming nearly out of batteries), has reverted to acollapsed configuration so that it has sunk below the surface of thewater except for a hook 23 which extends above the surface of the water.The UAV is equipped with some communication means (e.g., a recoverybeacon or Wi-Fi and GPS) which enables the UAV to be located by a WPV.When contact with the recovery cable 120 is detected, the hook isclosed. In FIG. 6, the hook is shown adjacent to, and ready to engage,the recovery cable extending from the WPV, so that the UAV can berecovered by the WPV.

FIG. 6 shows a float which can be part of a WPV and which includes abattery 50 having tubes 55 for launching a collapsed UAV from the float.

FIG. 7 shows a float which can be part of a WPV, and an auxiliary float60 which is connected to the WPV by a cable 61 and which includes abattery 50 having tubes 55 for launching a collapsed UAV from theauxiliary float.

What is claimed is:
 1. A float which comprises means for launching anunmanned aerial vehicle (UAV).
 2. A wave-powered vehicle (WPV) ashereinbefore defined which comprises a float according to claim
 1. 3. Awave-powered vehicle (WPV) which comprises means for recovering anunmanned aerial vehicle (UAV) which is floating in the water.
 4. A floatwhich comprises means for recovering an unmanned aerial vehicle (UAV)which is floating in the water.
 5. A method, performed by a wave-poweredvehicle (WPV) having communications equipment, of monitoring vesselswhich are floating in water, the method comprising: receivingcommunications from an unmanned aerial vehicle (UAV) on thecommunications equipment of the WPV; and transmitting correspondingcommunications to a receiving station at a remote location.
 6. A methodof monitoring a vessel which is floating in water, the methodcomprising: correlating signals received by a plurality of WPVs toidentify the location of the vessel; and launching a UAV from a WPVaccording to claim
 2. 7. An unmanned aerial vehicle (UAV) which, when itlands on water, sinks below the surface of water except for a recoverymeans which remains above the surface of the water.
 8. An unmannedaerial vehicle (UAV) which can be converted between (1) a collapsed formin which it can be stowed in a tube and (2) an unfolded form which canoperate as a UAV and which the UAV adopts automatically when it isreleased from the tube.
 9. A float comprising: a hull; a launch tubemounted to the hull for storing a UAV according to claim 8 when the UAVis in its collapsed form; and means for ejecting the collapsed UAV fromthe launch tube whereupon the UAV, when ejected, adopts its unfoldedform.
 10. The float of claim 9, and further comprising elements forproviding wave-powered propulsion to the float so that the float is acomponent of a wave-powered vehicle (WPD).